The focus of this grant is training in basic research. A two year multidisciplined plan of didactic and technical instruction in cell, molecular, and developmental biology has been formulated to be followed by an intensive three year guided research experience in the field of craniofacial development. The applicant is a dental clinician who has completed specialty training in orthodontics. Implementation of this proposal will provide the applicant with a research background of sufficient breadth and strength to allow him to pursue a career as a productive biomedical investigator, consistent with the goals of the Physician Scientist Award. The training plan (Phase I) includes (1) intensive hands on work in molecular biology in cosponsor Bjorn Olsen's laboratory. In addition to in situ hybridization, I will learn quantitative methods of molecular genetics as applied to the isolation and analysis of cartilage collagen genes. (2) I will learn cutting edge cell labeling techniques with Drs. Hay, Gallop, and Shankland in order to trace the fate of medial edge epithelium (MEE) during palate fusion in organ culture. (3) I will acquire expertise in morphological techniques such as immunohistochemistry. The research (Phase II) focuses on the mechanism of epithelial mesenchymal transformation. The animal model for this study will be the rat embryo. A combination of morphological as well as developmental and molecular biological techniques are proposed to document changes in the MEE as palate fusion process proceeds to confluence. Ultrastructural evidence is presented which suggests that, rather than dying as currently believed, the basal cells of the MEE transform into mesenchyme when the palatal shelves fuse. If I do not prove this hypothesis in Phase I, I will present a plan to study facial neural crest in Phase II. As planned here, Phase II has 4 components: 1) Does gene expression change in the cells of the basal cell layer of the MEE as these cells transform during palatal fusion? 2) Is cell proliferation required for epithelial mesenchymal transformation? 3) What is the role, if any, of the mesoderm in the transformation of the basal cells of the MEE to the mesenchymal cell type? 4) What is the role, if any, of extracellular matrix in this process? Not only will these studies help us to understand epithelial- mesenchymal transformation, but also the hypothesis presented, if correct, will result in reinterpretation of and different approaches to studies of palate development.